This is clear and useful but I wish you'd picked different example numbers. Using 1 and 2 for both bread and milk makes it harder to look at the matrix form and immediately see whether a 1 in a matrix is the bread 1 or the milk 1. If you could use 1,2,3,4 instead of 1,2,1,2 it would make things much clearer.
I agree with this critique because, with learning linear algebra, there are a lot of numbers flying around and the order of them is very important. This is why I like to use the prime sequence for my example numbers, because you can also see where they contributed to results of multiplication operations.
Agreed completely when ever I need random example sequences it is often sequences of primes or some subset like even indexed primes (meaning 2, 5, 11, ...) mixed with odd indexed (primes 3, 7, 13...) when dealing with complex numbers, or every fourth if I want two sequences of complex numbers. The only trouble is they do start going pretty large.
